(1) Field of the Invention
This invention relates to novel muramyl peptide derivatives. The muramyl peptide derivatives can act on immunological mechanisms(especially on cells relevant to immune responses)in the living body of mammals including human being and are useful as immunomodulators.
(2) Description of the Prior Art
It is known that muramyl peptides possess a wide variety of biological activities.
As their in vitro activities, there are (a) activity on cells relevant to immune response (e.g., monocytes and macrophages, B lymphocytes, T lymphocytes, natural killer cells or the like); (b) activity on other cells (e.g., thrombocytes, fibroblasts, osteoclasts or the like); (c) activation of complementary system and so forth. As in vivo activities, there are (a) modulation of immune responses; (b) increase of natural resistance against microbial infections and tumor development, and so forth [see S. Kotani and H. Takada: Immunopharmacological activities of bacterial cell walls and related synthetic compounds (muramyl peptides), YAKUGAKU ZASSHI, 103(1), ppl - 27(1983)]. Known muramyl peptides are e.g., B30-muramyl dipeptide [S. Kusumoto et al, Tetrahedron Lett. 49, pp4899-4902(1978)], muramyl dipeptidelysin (K. Matsumoto et al., Immunostimulants, Now and Tomorrow p79-97, Japan Sci. Soc. Press, Tokyo, 1987), and those disclosed in Japanese patent unexamined publication Nos. -172399, 59-20297 and 61-275299.
There is still need for other compounds having excellent activities than known muramyl peptide derivatives.